Water-based polymer emulsions for opaque films and coatings applications on flexible substrates

ABSTRACT

A process of preparing a water-based emulsion includes adding a first monomer feed to a reaction vessel in the presence of a first initiator and water to form an acid-functional polymer; neutralizing the acid-functional polymer to form a particulate polymer; and adding a second monomer feed to the reaction vessel in the presence of a second initiator to form an agglomerated polymer; where the process is a one-pot process. The first monomer feed includes a unbranched (meth)acrylate monomer, a (meth)acrylic acid monomer, a branched (meth)acrylate, and a styrenic monomer; the second monomer feed includes a hydrophobic monomer; the water-based emulsion includes the agglomerated polymer; the agglomerated polymer includes the particulate polymer; and the agglomerated polymer having an aggregated drupelet morphology. The agglomerated polymers may be used in high opacity emulsions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. 371 National Stage Application of PCTInternational Application No. PCT/US2012/052831, filed on Aug. 29, 2012,which claims the benefit of U.S. Provisional Patent Application No.61/529,011, filed on Aug. 30, 2011, the contents of both of which areincorporated herein by reference in their entirety for any and allpurposes.

FIELD

The present technology generally relates to polymer-based coatingshaving high opacity.

BACKGROUND

Water-based emulsions leading to high opacity films and coatings are ofinterest for applications in various fields such as paints, inks,automotive coatings, fillers, etc. where hiding or opacity is required.In order to improve opacity in polymer emulsions, various approacheshave been suggested such as incorporating inorganic materials (titaniumdioxide, silicon dioxide, etc.) within the polymer or incorporation ofair domains (hollow spheres) within the polymer particle to incorporatecontrast of refractive indexes within the coating materials.

SUMMARY

In one aspect, a process of preparing a water-based emulsion having anagglomerated polymer includes adding a first monomer feed to a reactionvessel in the presence of a first initiator and water to form anacid-functional polymer; neutralizing the acid-functional polymer toform a particulate polymer; and adding a second monomer feed to thereaction vessel in the presence of a second initiator to form theagglomerated polymer; wherein the process is a one-pot process; thefirst monomer feed includes a unbranched (meth)acrylate monomer, a(meth)acrylic acid monomer, a branched (meth)acrylate, and a styrenicmonomer; the second monomer feed includes a hydrophobic monomer andoptionally a (meth)acrylate monomer; the agglomerated polymer includesthe particulate polymer; and the agglomerated polymer has a drupeletmorphology. In one embodiment, the particulate polymer has an averageparticle size of from about 1 nm to about 1000 nm. In any of the aboveembodiments, the agglomerated polymer may have an average particle sizeof from about 200 nm to about 3000 nm.

In any of the above embodiments, the unbranched (meth)acrylate monomerincludes methyl methacrylate, ethyl methacrylate, n-propyl methacrylate,n-butyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate,2-n-butoxyethyl methacrylate, 2-chloroethyl methacrylate, trifluoroethylmethacrylate, benzyl methacrylate, cinnamyl methacrylate, 2-ethoxyethylmethacrylate, n-octyl methacrylate, 2-phenoxyethyl methacrylate,2-phenylethyl methacrylate, propargyl methacrylate, methyl acrylate,ethyl acrylate, n-propyl acrylate, n-butyl acrylate, n-amyl acrylate,n-hexyl acrylate, 2-n-butoxyethyl acrylate, 2-chloroethyl acrylate,trifluoroethyl acrylate, benzyl acrylate, cinnamyl acrylate,2-ethoxyethyl acrylate, n-octyl acrylate, 2-phenoxyethyl acrylate,2-phenylethyl acrylate, or propargyl acrylate. In any of the aboveembodiments, the (meth)acrylic acid monomer includes acrylic acid ormethacrylic acid. In any of the above embodiments, the branched(meth)acrylate monomer includes isopropyl methacrylate, isobutylmethacrylate, isoamyl methacrylate, 2-hydroxyethyl methacrylate,2-hydroxypropyl methacrylate, sec-butyl methacrylate, tert-butylmethacrylate, 2-ethylbutyl methacrylate, cyclohexyl methacrylate,cyclopentyl methacrylate, furfuryl methacrylate, hexafluoroisopropylmethacrylate, 3-methoxybutyl methacrylate, 2-methoxybutyl methacrylate,2-nitro-2-methylpropyl methacrylate, n-octyl-methacrylate, 2-ethylpentylmethacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate,tetrahydrofurfuryl methacrylate, tetrahydropyranyl methacrylate,isopropyl acrylate, isobutyl acrylate, isoamyl acrylate, 2-hydroxyethylacrylate, 2-hydroxypropyl acrylate, sec-butyl acrylate, tert-butylacrylate, 2-ethylbutyl acrylate, cyclohexyl acrylate, cyclopentylacrylate, furfuryl acrylate, hexafluoroisopropyl acrylate,3-methoxybutyl acrylate, 2-methoxybutyl acrylate, 2-nitro-2-methylpropylacrylate, n-octyl-acrylate, 2-ethylpentyl acrylate, 2-ethylhexylacrylate, phenyl acrylate, tetrahydrofurfuryl acrylate, ortetrahydropyranyl acrylate. In any of the above embodiments, thehydrophobic monomer includes styrene or α-methylstyrene. In any of theabove embodiments, the first and second initiators individually includeammonium persulfate, potassium persulfate, sodium persulfate, tert-butylhydroperoxide and dicumyl peroxide.

In any of the above embodiments, the neutralizing includes adding a baseto the particulate polymer. In such embodiments, the base may includeammonia, sodium hydroxide, potassium hydroxide, methylamine,triethylamine, ethanolamine, or dimethylethanolamine.

In any of the above embodiments, the first monomer feed may be added inthe absence of a surfactant.

In any of the above embodiments, the process may further include addingone or more of a surfactant, biocidal agent, dispersant, pigment,fillers, defoamer, wetting agent, light stabilizer, surface-activeagent, thickener, or pigment stabilizer to the agglomerated polymer. Inany of the above embodiments, the adding of the first monomer feed isconducted at a temperature from about 30° C. to about 100° C.

In any of the above embodiments, the particulate polymer has at least afirst glass transition temperature of greater than 30° C. In someembodiments, the agglomerated polymer has at least a first glasstransition temperature of greater than −20° C. and a second glasstransition temperature of greater than 80° C. In some embodiments, theagglomerated polymer has at least a first glass transition temperatureof from about −20° C. to about 50° C. and a second glass transitiontemperature of from about 80° C. to about 150° C. In some embodiments,the agglomerated polymer has at least a first glass transitiontemperature of from about 10° C. to about 40° C. and a second glasstransition temperature of from about 80° C. to about 120° C.

In another aspect, agglomerated polymer particles produced by any of theabove processes, are provided.

In another aspect, an agglomerated polymer particle is provided thatincludes two or more primary polymer particles wherein the agglomeratedpolymer has an aggregated drupelet morphology. In some embodiments, theprimary polymer particles include a neutralized(meth)acrylate—(meth)acrylic acid—styrenic co-polymer. In someembodiments, the two or more primary polymer particles are sequesteredin the agglomerated polymer particle by a hydrophobic polymer. In someembodiments, the hydrophobic polymer is a styrenic polymer. In someembodiments, the particles have an average particle size of from about200 nm to about 3000 nm. In some embodiments, the particles have anaverage particle size of from about 200 nm to about 700 nm. In someembodiments, the primary polymer particles have an average particle sizeof from about 1 nm to about 100 nm.

In another aspect, a coating is provided including an agglomeratedpolymer particle including two or more primary polymer particles whereinthe agglomerated polymer has an aggregated drupelet morphology. In someembodiments, the coating may further include a surfactant, a biocidalagent, a drying agent, a dispersant, a pigment, a filler, a defoamer, awetting agent, a light stabilizer, a surface-active agent, a thickener,a or a pigment stabilizer. In some embodiments, the agglomerated polymerparticle is prepared by any of the above processes.

In another aspect, an emulsion is provided, the emulsion including anagglomerated polymer particle having a drupelet-like morphology andincluding a primary particle phase having a surfactant-freepolymerization product of an unbranched (meth)acrylate monomer, a(meth)acrylic acid monomer, a branched (meth)acrylate monomer, and astyrenic monomer; and a secondary particle phase having a polymerizationproduct of a styrenic monomer, and, optionally, a (meth)acrylatemonomer, where the primary particle phase has a smaller dimension thanthe secondary particle phase. In any of the emulsion embodiments, theprimary particle phase may have an average particle size of from about 1nm to about 1000 nm. This may include an average particle size of fromabout 200 nm to about 3000 nm. In any of the emulsion embodiments, theprimary particle phase may have at least a first glass transitiontemperature of greater than −20° C. This may include the agglomeratedpolymer particle having at least a first glass transition temperature ofgreater than −20° C. and a second glass transition temperature ofgreater than 80° C.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B are SEM images of a dried, opaque particle emulsionaccording to the examples.

FIGS. 2A and 2B are AFM images of a dried, opaque particle emulsionaccording to the examples. FIG. 2A is a height image and FIG. 2B is aphase image.

FIG. 3A is an illustration of a surfactant-free emulsionco-polymerization of hydrophobic and hydrophilic containing monomersleading to phase separation within the particle, according to variousembodiments.

FIG. 3B is an illustration of the neutralization of the product preparedaccording to FIG. 3A, where the smaller sized hydrophilic polymer phase(smaller particles) migrate from the internal part of the particles tothe surface of the polymers (to the water-polymer interface), accordingto various embodiments.

FIG. 3C is an illustration of the final stage of the polymerization fromFIGS. 3A and 3B, wherein the polymerization with further hydrophobicmonomer results in further growth of particle sizes resulting in largesized raspberry structured particle agglomerates, according to variousembodiments.

FIG. 4 is an illustration of a coating, produced with the agglomeratedpolymer particles, interacting with light to show the scatteringpotential, according to various embodiments.

FIG. 5 is a DSC trace for Example 4.

FIG. 6 is a DSC trace for Example 5.

FIG. 7 is a dual axis graph for Examples 1-5 comparing opacity,adhesion, and water-resistance for the examples.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part thereof. The illustrativeembodiments described in the detailed description, drawings and claimsare not meant to be limiting. Other embodiments may be utilized, andother changes may be made, without departing from the spirit or scope ofthe subject matter presented here. The present technology is alsoillustrated by the examples herein, which should not be construed aslimiting in any way.

In one aspect, a process is provided for the synthesis of water-basedemulsions for the use in high opacity films and coatings. The processincludes a one-pot synthesis in at least two stages. The first stageincludes water-based polymerization of an acid functional (i.e.hydrophilic) monomer and polymerization of a hydrophobic monomer, in theabsence of a surfactant. Neutralization of the acid-functional polymerwith a base is then followed by a second stage of polymerization withadditional hydrophobic monomer(s). The second stage includes adding aninitiator and a hydrophobic monomer, thereby starting a secondpolymerization process that produces a second polymer comprising theparticulate polymer. Addition of a non-ionic surfactant during or at theend of feed 2 helps stabilize the emulsions. This second polymer istermed an agglomerated polymer.

The one-pot process results in the polymer particles agglomerating intocomposite particles having an aggregated drupelet morphology. As usedherein, a one-pot process is defined as a multi-step reaction, where allreaction steps are conducted in the same reaction vessel. In the aboveone-pot process, both first and second stages occur in the same reactionvessel. Such a one-pot process is more efficient in terms of requiredequipment, cost, and consistency of the process and eventual product.

As used herein, an aggregated drupelet morphology is defined asresembling the surface of a raspberry or blackberry. As illustrated inFIGS. 1A, 1B, 2A, and 2B, the surface of the aggregated polymerresembles the surface of a raspberry or blackberry in that there areindividual bumps or particles joined into a single, larger particle, andfor which at least some of the individual members are readilydiscernable on the surface of the larger particles. The structuresillustrated in FIGS. 1A, 1B, 2A, and 2B are more fully described below.

Coatings prepared with emulsions of the agglomerated drupelet particlesexhibit an increased opacity, as compared to coatings that are notprepared with such particles. Without being bound by theory, it isbelieved that the agglomerated drupelet particles provide increasedopacity due to one or more of the particles size of the agglomerateddrupelet particles, the presence of air voids in the coating, or theincreased pigment dispersability. For example, larger particle sizes ofthe agglomerated drupelet particles cause greater amount of lightscattering in coatings. Additionally, the non-spherical nature ofparticles prevents tight packing of the particles in a coating, therebycausing air voids in the coatings. The presence of air voids in thecoatings result in greater scattering of light due to higher contrast inrefractive index between polymer and air, compared to polymer andpolymer. Finally, the morphology of the latex particles may assist inthe dispersability of the pigment particles, resulting in a morehomogeneous distribution of the pigment within the coating. Theagglomerated morphology of the particles having small hydrophilicdomains on the surface of the larger agglomerated particles is believedto act as an effective pigment dispersant leading to the betterdispersability of the pigment particles. The better the dispersion ofpigment particles within the coating results in more distributedscattering centers (pigment particles) per unit volume of the coatingresulting in higher scattering of light and improved opacity.

As noted above, the process includes at least two stages. The firststage includes the product of the free radical polymerization of atleast two different (meth)acrylate monomers (hydrophilic monomers) andstyrene (hydrophobic monomer) by adding a water-soluble initiator toproduce smaller particle dispersions stabilized in water. The at leasttwo different hydrophilic monomers are a non-branched (meth)acrylate anda branched (meth)acrylate. The branched (meth)acrylate provides for alower glass transition temperature for the hydrophilic polymer particlesas opposed to those prepared without the branched (meth)arylate, therebyimparting flexibility to coatings prepared with the emulsions.

The lower glass transition temperature of the hydrophilic polymerprovides for better adhesion of the polymer particles to plastics.Accordingly, emulsions of such particles may be used to prepare coatingsfor plastics, flexible substrates, and flexible packaging. Illustrativeplastics include, but are not limited to, polyethylene, polypropylene,polyurethanes, polyesters, and polycarbonates.

After the end of first feed, a base neutralizes the acid-functionaldispersion. The polymerization of the first stage, followed by theneutralization step, results in the formation of drupelet-like particlesthat act as a seed for the second stage polymerization. Duringneutralization, the acid-rich phases become more water-soluble(hydrophilic) due to salt-formation resulting in migration of theneutralized acid-rich domains onto the surface of the multiphasicparticles. The second stage includes the addition of further initiatorand monomer to start a second polymerization, which leads to formationof larger drupelet-like particles. This technique results in emulsionswith larger sized particles (e.g. >400 nm) with the morphology of araspberry-type structure. A non-ionic surfactant may be added to theemulsion during, or at the end of, the second stage.

The general process is shown in the illustration presented in FIG. 3. InFIG. 3, a reaction vessel 10 is illustrated containing water 20 and anagitation or stirring apparatus 30 to form polymer particles 40,according to the first stage of the reaction. The first stage of thereaction is carried out as a surfactant-free emulsion polymerization ofa hydrophilic monomer and a hydrophobic monomer. The hydrophilic andhydrophobic monomers polymerize to form polymer domains that arehydrophilic (acid-rich) 60 and hydrophobic (acid-poor) particles 50. Thestoichiometry of the reaction is such that the hydrophobic domain 50surrounds the hydrophilic domain 60 during the first stage.

After formation of the polymer particles under the surfactant-freeconditions, the emulsion polymerization is neutralized by addition of abase, in a second stage. FIG. 3B illustrates the neutralization stagewhere the polymer particles 40 undergo an internal shift of thehydrophobic 50 and hydrophilic 60 domains. During neutralization, thehydrophilic phase 60 reacts with added base to form a neutral phase 70.After neutralization, the neutralized particles 70 are able to migrateto the surface of the hydrophilic particles 50, thereby forming adrupelet-like morphology. Further hydrophobic monomer addition resultsin further growth of the polymer particles (FIG. 3C).

When the first stage results in low molecular weight polymers in thehydrophobic phase, the hydrophilic particles are able to migrate intothe water phase. Such polymerizations result in bi-modal size particles.That is, there are individual hydrophobic and hydrophilic particles inthe product. However, when the molecular weight of the hydrophobic phaseis high, the hydrophobic phase provides for adsorption of thehydrophilic particles to the surface of the hydrophobic phase, and intoan agglomerated particle, having an overall rather uniform particlesize. The increase in molecular weight of the hydrophobic phase preventsthe neutralized hydrophilic phase (smaller particles) from beingcompletely detached from the particle, resulting in the formation ofaggregates that have a drupelet-like surface morphology. The morphologyresembles that of a blackberry or raspberry, not only in shape but alsoin surface definition, with at least a portion of the surface of atleast some of the smaller polymer particles protruding from the surfaceto give the surface the characteristic “bumpy,” “raspberry-like,” or“blackberry-like” appearance.

As will be apparent, the hydrophilic polymer particles formed in thefirst stage are necessarily smaller than the agglomerated polymerparticles. According to one embodiment, the hydrophilic particulatepolymer prepared in the first stage has an average particle size of fromabout 1 nm to about 700 nm. In some embodiments, the hydrophilic polymerparticles have an average size from about 50 nm to about 700 nm. In someembodiments, the hydrophilic polymer particles have an average size fromabout 50 nm to about 250 nm. In some embodiments, the hydrophilicpolymer particles have an average size from about 50 nm to about 100 nm.The agglomerated polymer particles may have an average particle size offrom about 100 nm to about 3 μm. For example, in one embodiment, theagglomerated polymer particles have an average particle size of fromabout 200 nm to about 1 μm. In other embodiments, the agglomeratedpolymer particles have an average particle size of from about 300 nm toabout 700 nm. In some embodiments, the agglomerated polymer particlescontain at least two of the polymer particles of the first stage.

Without being bound by theory, it is believed that it is theagglomerated drupelet morphology that produces the desired opacity ofthe present materials, when they are employed in a coating capacity.Opacity in films is controlled by the amount of light that is scatteredby the particles within the film, and the contrast in the refractiveindices of the different mediums within the films. The drupelet-likemorphology assists in causing large amounts of scattering and thusproviding higher opacities. As illustrated in FIG. 4, when incidentlight beams 5, 6 interact with the surface of the particles in thecoating at different points, the light is reflected, and scatteringoccurs. The scattering results in a loss of optical clarity and anopaque appearance of the coating. Other physical features of the coatingand agglomerated polymer particles also have a bearing on the degree ofopacity. For example, polymer particles that remain discreet polymerparticles at operating temperatures of the coating provide for greateropacity.

The hydrophilic polymer particles and the hydrophobic polymer particleshave different glass transition temperatures (Tg), when measured using adifferential scanning calorimeter (DSC). The different Tg for the twophases is indicative of the phase separation within the particle. Insome embodiments, the hydrophobic polymer of the agglomerated polymerparticles and particulate polymers have T_(g) (glass transitiontemperature) values that are greater than the highest temperature towhich the coating will be exposed. This may be a T_(g) greater than roomtemperature, or greater than 80° C., or even greater than 100° C. Insome embodiments, the hydrophobic polymer of the agglomerated polymerparticles has a T_(g) from about 80° C. to about 150° C. In some suchembodiments, the hydrophobic polymer of the agglomerated polymerparticles has a T_(g) from about 80° C. to about 125° C. In someembodiments, the hydrophobic polymer of the agglomerated polymerparticles has a T_(g) from about 75° C. to about 120° C.

The primary particles, i.e. the particulate polymers, may have adifferent T_(g) than the hydrophobic polymers, thereby providing for atwo-phase transition of the agglomerated polymer particles. In someembodiments, the primary particles may have a T_(g) that is greater the−20° C. Thus, in some embodiments, the primary polymer particles have aT_(g) from about −20° C. to about 50° C. In some such embodiments, theprimary polymer particles have a T_(g) from about 0° C. to about 50° C.In some such embodiments, the primary polymer particles have a T_(g)from about 10° C. to about 40° C. In some embodiments, the hydrophilicpolymer particles (the “primary particles”) have a T_(g) from about −20°C. to about 50° C., and the hydrophobic regions have a T_(g) from about75° C. to about 150° C. This includes embodiments, where the hydrophilicpolymer particles have a T_(g) from about 0° C. to about 40° C., and thehydrophobic regions have a T_(g) from about 75° C. to about 120° C.

Another physical feature of the coating and agglomerated polymerparticles that has a bearing on the degree of opacity is the number andsize of the void areas between the particles. Void areas betweenparticles are those areas that are not filled by particles, due to theparticle shape. Reference number 15 in FIG. 4 describes illustrativevoid areas. To the extent that light is able to pass through enough ofthe coating and particles to encounter a void area, the void areaprovides additional surfaces on which the light may be reflected andscattered. Further scattering may then occur in reflected light as itattempts to exit the coating, or is refracted through the coating. Thevoid areas are created due to the irregular packing of the particles asthey are applied in a coating to the surface of a substrate, and as thecoating cures on the surface. The irregular shapes of the agglomeratedpolymer particles leads to irregular packing and a more randomizedsurface to enhance light scattering. More void areas leads to greateropacity.

The high opacity and hiding ability of coatings employing theagglomerated polymer particles is attributed to the polymers andmorphologies described. Additives or pigments that are traditionallyused for increasing the opacity and hiding ability of a coating are notrequired, although they may be used. However, exclusion of suchadditives may provide for lower cost coatings.

Opacity, as used herein, is defined as the ability of a coating toprevent the transmission of light. To quantify and compare opacity orhiding power of the various emulsions and their coating(s), contrastratios of the dried coating(s) were measured on Leneta cards (contrastof the coating between white and black background). The opacity was thenrated visually on a scale of 0-5 with 5-being best in opacity and 0being worst in opacity. Coatings using the agglomerated particlesemulsions typically exhibit a contrast ratio on Leneta card of greaterthan 30% (contrast ratio ranged between 10% and 80%) and visual ratingof greater than or equal to 4.

In the first stage of the two-stage process, at least a first and asecond acrylate and/or (meth)acrylate monomer (i.e. hydrophilicmonomers), and a styrenic monomer (i.e. hydrophobic monomer) are addedto a reaction vessel (i.e. the pot) in an aqueous medium in the presenceof a free-radical initiator. The second stage also includes addition ofa styrenic monomer, and optionally a minor amount of a branched orunbranched (meth)acrylate monomer.

Suitable unbranched (meth)acrylate monomers for use in the monomeraddition of the first stage include, but are not limited to, methylmethacrylate, ethyl methacrylate, n-propyl methacrylate, n-butylmethacrylate, n-amyl methacrylate, n-hexyl methacrylate, 2-n-butoxyethylmethacrylate, 2-chloroethyl methacrylate, trifluoroethyl methacrylate,benzyl methacrylate, cinnamyl methacrylate, 2-ethoxyethyl methacrylate,n-octyl methacrylate, 2-phenoxyethyl methacrylate, 2-phenylethylmethacrylate, propargyl methacrylate, methyl acrylate, ethyl acrylate,n-propyl acrylate, n-butyl acrylate, n-amyl acrylate, n-hexyl acrylate,2-n-butoxyethyl acrylate, 2-chloroethyl acrylate, trifluoroethylacrylate, benzyl acrylate, cinnamyl acrylate, 2-ethoxyethyl acrylate,n-octyl acrylate, 2-phenoxyethyl acrylate, 2-phenylethyl acrylate, andpropargyl acrylate.

Suitable branched (meth)acrylate monomers for use in the monomeraddition of the first stage include, but are not limited to, isopropylmethacrylate, isobutyl methacrylate, isoamyl methacrylate,2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, sec-butylmethacrylate, tert-butyl methacrylate, 2-ethylbutyl methacrylate,cyclohexyl methacrylate, cyclopentyl methacrylate, furfurylmethacrylate, hexafluoroisopropyl methacrylate, 3-methoxybutylmethacrylate, 2-methoxybutyl methacrylate, 2-nitro-2-methylpropylmethacrylate, n-octyl-methacrylate, 2-ethylpentyl methacrylate,2-ethylhexyl methacrylate, phenyl methacrylate, tetrahydrofurfurylmethacrylate, tetrahydropyranyl methacrylate, isopropyl acrylate,isobutyl acrylate, isoamyl acrylate, 2-hydroxyethyl acrylate,2-hydroxypropyl acrylate, sec-butyl acrylate, tert-butyl acrylate,2-ethylbutyl acrylate, cyclohexyl acrylate, cyclopentyl acrylate,furfuryl acrylate, hexafluoroisopropyl acrylate, 3-methoxybutylacrylate, 2-methoxybutyl acrylate, 2-nitro-2-methylpropyl acrylate,n-octyl-acrylate, 2-ethylpentyl acrylate, 2-ethylhexyl acrylate, phenylacrylate, tetrahydrofurfuryl acrylate, and tetrahydropyranyl acrylate.Suitable (meth)acrylic acid monomers include, but are not limited to,acrylic acid and methacrylic acid.

As used herein, the “meth” in parentheses before acrylic or acrylate isused to designate either the methacrylic or acrylic, or the methacrylateor acrylate compound. Suitable styrenic monomers for use in the monomeraddition of the first or second stages include, but are not limited to,styrene and α-methylstyrene. Suitable (meth)acrylates that mayoptionally be added during the second stage include the unbranched andbranched (meth)acrylates described above. One (meth)acrylate that mayoptionally be used in the second stage is ethylhexylacrylate.

As noted above, after the first stage is complete, a base is added. Theaddition of the base is intended to neutralize the acid functionalpolymer that is produced in the first stage. Suitable bases include, butare not limited to, ammonia, sodium hydroxide, potassium hydroxide,methylamine, triethylamine, ethanolamine, and dimethylethanolamine. Thebase may be added in less than stoichiometric amounts, or instoichiometric amounts or in an amount that is a slight stoichiometricexcess. The partial, or complete, neutralization of the acid-containingfirst stage polymer results in some, or all, of the polymer particlesgenerated in the first stage polymer to increase in their hydrophiliccharacter. The second stage of polymerization of the hydrophobic polymerfollowing the base neutralization of the first stage polymer results intwo different polymer particles species that are sequestered togetherforming the agglomerated particle.

As noted above, a non-ionic surfactant may be added to the emulsionduring, or at the end of, the second stage. Such surfactants during thesecond stage may assist in stabilizing the emulsion. Suitable non-ionicsurfactants include, but are not limited to, polyethylene glycolpolymers, or poly(ethylene oxide-propylene oxide) co-polymers availablecommercially under tradenames such as Pluronic®, Tetronic®, Surfynol®,and Pluracol®.

The initiators used in either the first stage or the second stage may bethose as are commonly used for free-radical polymers and which are watersoluble. Suitable initiators include, but are not limited to, ammoniumpersulfate (APS), potassium persulfate (PPS), sodium persulfate,tert-butyl hydroperoxide (TBHP), dicumyl peroxide, hydrogen peroxide,and the like.

Other additives that may then be added to the emulsions includeadditives such as, but not limited to, surfactants, biocidal agents;drying agents; dispersants; pigments; fillers such as a clay, calciumcarbonate, and the like; defoamers; wetting agents; light stabilizers;surface-active agents; thickeners; and pigment stabilizers. As usedherein, biocidal agents are materials that prevent or inhibit the growthof bacteria, viruses, fungi, or other biological fouling agents in theemulsions or products prepared with or from such emulsions. As usedherein, drying agents, are materials added to a coating or emulsion toenhance the drying speed of the coating. As used herein, dispersants arematerials that are added to a coating or emulsion to prevent or minimizesetting of the emulsions or coatings after formation. As used herein,light stabilizers prevent, or minimize, degradation of the polymers byexposure to various light sources, including ultra violet light. As usedherein, surface-active agents are materials that are added to theemulsion in order to stabilize emulsions. As used herein, thickeners arematerials that are added to the emulsion to increase the viscosity ofthe emulsion. As used herein, pigment stabilizers are materials that areadded to stabilize a pigment from fading and degradation.

According to one embodiment, the first stage of the process is conductedat elevated temperature. For example, the temperature may range fromabout 30° C. to about 100° C. In some embodiments, the temperature atwhich the first stage is conducted is from about 60° C. to about 90° C.The second stage may be conducted in similar temperature ranges. In someembodiments, the second stage is conducted at substantially the sametemperature as the first stage. This is noted to be “substantially,”because, as those of skill in the art will understand, the temperatureof the reaction vessel during addition of monomers, additional water, orother additives, may fluctuate slightly over time, or due to variationin thermostatted heating devices or baths.

The weight average molecular weight (M_(w)) of the polymer particlesproduced in the first stage of the process is from about 5,000 g/mol toabout 1,000,000 g/mol. In some such embodiments, the M_(w) of thepolymer particles produced in the first stage of the process is fromabout 200,000 g/mol to about 300,000 g/mol. The M_(w) of the hydrophobicpolymer in the agglomerated polymer particles produced in the secondstage of the process is from about 5,000 g/mol to about 1,000,000 g/mol.In some such embodiments, the M_(w) of the hydrophobic polymer in theagglomerated polymer particles produced in the second stage of theprocess is from about 200,000 g/mol to about 300,000 g/mol.

As will be observed from the examples, the process may include one ormore holding, or equilibration, periods. Such periods may range from aminute or two to several minutes or hours. The holding, orequilibration, periods (the terms are used interchangeably), are forallowing completion of the reaction and/or for allowing the reactionmixture to be homogeneously dispersed.

In view of the neutralization of the acid functional polymer particlesin the first stage, and the polymerization of a non-acid functional,hydrophobic monomer in the second stage, the final pH of the emulsionthat is produced in the process is near neutral. In some embodiments,the pH of the water-based emulsion that is produced is from about 6 toabout 8. In some such embodiments, the pH is from about 7 to about 7.5.

After the reaction is completed and the reaction mixture is cooled toroom temperature, the emulsion is filtered.

Because the water-based emulsions are to be used in coatings, accordingto one embodiment, the viscosity of the water-based emulsion is oneparameter that may be monitored or adjusted to provide for differentflow rates, application conditions, and the like. Increasing the solidscontent of the water-based emulsion may increase the viscosity, orthickeners may be added to the emulsion to provide an increase inviscosity. In either event, the viscosity may be targeted to a valuefrom about 50 cps to about 2,000 cps.

In another aspect, the agglomerated polymers described above areprovided. As noted above, the agglomerated polymer particles have both aprimary structure and a secondary structure. The primary structure isthe particulate polymer formed during the first stage and includes aneutralized (meth)acrylate—(meth)acrylic acid—styrenic co-polymer havinga small particle size. During the second stage the secondary structureis formed and includes agglomeration of the primary particles into anaggregated drupelet morphology. FIGS. 1A and 1B include scanningelectron microscope (SEM) images of the agglomerated particles, withFIG. 1B being a magnification of FIG. 1A. The surface detail of theparticles is illustrated in the atomic force microscope (AFM) images ofFIGS. 2A and 2B. As described above, and without being bound by theory,it is believed that such a surface provides the basis for the opacity ofsuch polymers when used as a coating, without the need for additionalhiding or whitening pigments or other additives present.

Accordingly, in one embodiment, an agglomerated polymer particle isprovided, including a host, hydrophobic polymer and at least two smallerpolymer particles, where the agglomerated polymer particle having anaggregated drupelet morphology.

Emulsions of any of the above prepared agglomerated polymer particlesare also provided. The emulsions may include an agglomerated polymerparticle having a drupelet-like morphology. The agglomerated polymerparticles include a primary particle phase that is the surfactant-freepolymerization product of an unbranched (meth)acrylate monomer, a(meth)acrylic acid monomer, a branched (meth)acrylate monomer, and astyrenic monomer; and a secondary particle phase that is thepolymerization product of a styrenic monomer, and, optionally, a(meth)acrylate monomer. These agglomerated polymer particles are thoseas described above having the dimensions, molecular weights, and glasstransition temperatures discussed above.

In another aspect a coating is provided that includes the agglomeratedpolymer particles described above. The coating may be a paint, an ink,primer, sizing agent, overprint varnish, or other like coating. Thecoatings provides for a high opacity without the addition of otheropacity enhancing additives such as pigments. However, such opacityenhancing additives may be included in coating formulations to furtherenhance the opacity, whitening, or hiding effects of the coating. Suchcoatings may include agglomerated polymer particles having a hydrophobicpolymer including at least two smaller polymer particles, theagglomerated polymer particle having an aggregated drupelet morphology.The coatings may also include dispersants, pigments or other additives.

The coatings may include a wide variety of additives such as, but notlimited to, surfactants, biocidal agents; drying agents; dispersants;pigments; fillers such as a clay, calcium carbonate, and the like;defoamers; wetting agents; light stabilizers; surface-active agents;thickeners; and pigment stabilizers, as described above. Pigments of allcolors and type may be used, as long as they are compatible with thewater-based emulsion coating.

Where the coating includes a pigment, the opaque coatings formed withthe agglomerated polymer particles exhibit an improvement in hiding. Forexample, where conventional water-based emulsions are used, coloredsubstrates tend to show through a single coating of the material,whereas where the opaque coatings are used, the show-through of thesubstrate is minimal or non-existent.

Such coatings may, of course, be applied to a substrate. Illustrativesubstrates include, but are not limited to, plastic, wood, concrete,ceramics, and glass. For example, the substrate may include, but is notlimited to, flexible plastic packaging, polypropylene, polyethylene,treated plastic, polycarbonates, treated or oxidized polypropylene,treated or oxidized polyethylene as substrates, and the like.

The present technology, thus generally described, will be understoodmore readily by reference to the following example, which is provided byway of illustration and is not intended to limit the present technology.

EXAMPLES Example 1

Water (38.30 g) was heated to 85° C. in a reactor with stirring. After15% of the first monomer feed (see Table 1) was added to the reactor,and a one minute hold, ammonium persulfate (APS; 0.17 g) dissolved inwater (1.55 g) was added to the reactor. After a wait period of 10minutes, the remainder of first monomer feed was added over a period of45 minutes. Upon completion of the addition of the monomer feed, thefeed tank was flushed with water (0.60 g). Ammonia (28% solution inwater, 1.05 g) diluted with water (3.73 g) was then added to the reactorover a period of 10 minutes, and the reactor was allowed to equilibratefor 2 minutes. Tert-butyl hydroperoxide (70% solution in water, 0.19 g)diluted with water (1.09 g) was then added to the reactor. A secondaddition of APS (0.25 g) dissolved in water (1.83 g) was then added tothe reactor. After a one minute hold, a second monomer feed (styrene18.89 g) was slowly added with stirring over a period of 70 minutes.After 55 minutes into the second monomer feed, Pluronic F-127 a feed ofPluronic F-127 solution (a ethylene oxide-propylene oxide polymer; 3.54g of a 13.2 wt. % solution in water) was fed into the reactor over 20minutes. Upon completion of the addition of the second monomer feed, themonomer feed tank was then flushed with water (0.60 g), followed by theF-127 solution tank with water (0.60 g). After 5 minutes, sodiumerythorbate (0.03 g) was then diluted with water (0.84 g) and added tothe reactor over 5 minutes and held for an additional 5 minutes. Thereaction was then allowed to start cooling and at 70° C., PluronicP-1200 (polyethylene glycol, 0.74 g), and Pluronic F-127 solution (aethylene oxide-propylene oxide polymer; 9.73 g of a 13.2 wt. % solutionin water) were added, followed by a flush with water (0.72 g). Afterholding for 15 minutes at 70° C., the reaction was cooled and at 50° C.,acticide MBS (preservative, 0.05 g) diluted with water (0.45 g), wasadded to the reactor. Cooling was then continued to room temperature andthe emulsion was filtered. Examples 2-5 were similarly prepared with thereactant amounts listed in Table 1.

Examples 2-7 were similarly prepared with the reactant amounts listed inTable 1.

TABLE 1 Reactant Amount For Examples 1-5. Reactant/Parameter Example (Inorder of reaction) 1 2 3 4 5 First Monomer Feed Ethyl acrylate (g) 5.135.24 5.13 4.82 4.56 Methacrylic acid (g) 2.53 2.59 2.53 2.83 2.25 MethylMethacrylate(g) 0.72 0.74 0.72 0.68 0.64 2-EHA (g) 2.17 4.44 6.52 6.127.73 Styrene (g) 4.33 4.42 6.50 6.10 5.78 APS/Water (g/g) 0.17/1.550.18/1.58 0.17/1.55 0.16/1.45 0.16/1.37 2^(nd) Monomer Feed APS/water(g/g) 0.25/1.83 0.25/1.87 0.25/1.83 0.23/1.71 0.22/1.62 Styrene (g)18.89  14.87  12.37  13.66  12.93  First Tg/Second Tg  36.9/102.8 26.8/102.9 26.6/99.3 23.0/98.9  12.0/100.1 (° C., DSC) First Tg/SecondTg 30.02/105   15.02/105   12.04/105   14.78/105   3.73/105  (° C.,Calc.*) *Calculated by the Fox-Flory Equation

Examples 1-3 was a ladder study by addition of 2-ethylhexyl acrylate tothe first monomer feed. By addition of 2-EHA, the T_(g) of the firstphase was lowered. The tape adhesion marginally increased across theseries until 3 where it significantly increased (Table 2). The opacityratings of Examples 1-3 were all sufficient. Examples 1-3 suggest thatthe lowering the Tg of phase 1 caused improved adhesion of the filmswhile giving a significantly large opacity advantage.

Based on the positive trend of adhesion, further reduction in the Tg ofthe first phase via addition of higher levels of 2-EHA in the first feedwas performed (Examples 4 and 5). Adhesion greatly improved while waterresistance and opacity were good (Table 2, below).

FIGS. 5 and 6 provide differential scanning calorimeter (DSC) data forExamples 4 and 5, respectively. The DSC traces clearly show 2 glasstransition temperatures for the samples. The hydrophilic particles havea Tg that is less than that of the hydrophobic particles.

Example 6

White Inks. White inks were prepare to a 21% pigment volumeconcentration by mixing Flexiverse® white dispersion WFD 5006 from SunChemical with the experimental emulsion from Table 1. The WFD 5006contains 65% TiO₂ pigment. The final ink solids was adjusted to 51-53%.The inks were drawn down with a K-0 rod with 4 micron wet film thicknesson clear linear low density polyethylene film. The prints were dried inan oven at 60° C. for one minute. Table 2 lists select properties of thefinal formulated inks

TABLE 2 Properties of White Inks Using the Emulsions from Table 1. WhiteInks Prepared With Example Test 1 2 3 4 5 Tape Adhesion Initial 1 2 2 43  1-Hour 1 2 4 4 4 24-Hours 1 2 4 5 5 Water Resistance  1 minute 4.5 54.5 2.5 2  5 minutes 4.5 5 4 3 1 10 minutes 2.5 4.5 4 3 1.5 30 minutes 24 3 2.5 1.5 60 minutes 1 2 3 3 1

FIG. 7 is a dual axis graph of all five of the above samples. In thegraph, the opacity is provided as a percentage on the left-hand axis,while the initial adhesion and 1 minute water resistance are on arelative 0-5 scale as shown on the right-hand axis. Water resistance isbased on one-hour spot test on the white film and were rated from 1-5 (1being worst and 5 being best). Tape adhesion is based on ink tapeadhesion test 1-5 (Scotch tape 610) Gloss was measured at 60 deg angleusing a gloss meter. The opacity measurements were performed bymeasuring the contrast ratio with a spectrophotometer by drawing downpigmented films on a Leneta card.

Based upon the above examples, it is apparent that softening of thesmaller particulate phase (phase 1) in RCD emulsion resulted inemulsions showing improved adhesion to plastics while maintaining theopacity in the films. Softening of phase 1 in RCD emulsion causes thecontinuous phase to coalesce and help film adhesion. To achieve thedesired opacity at same PVC, the emulsions presented herein allow for alessening in the amount of pigment due to the opacity increase of theparticles.

The present disclosure is not to be limited in terms of the particularembodiments described in this application. Many modifications andvariations can be made without departing from its spirit and scope, aswill be apparent to those skilled in the art. Functionally equivalentmethods, processes and compositions within the scope of the disclosure,in addition to those enumerated herein, will be apparent to thoseskilled in the art from the foregoing descriptions. Such modificationsand variations are intended to fall within the scope of the appendedclaims. The present disclosure is to be limited only by the terms of theappended claims, along with the full scope of equivalents to which suchclaims are entitled. It is to be understood that this disclosure is notlimited to particular methods, processes, reagents, compoundscompositions or biological systems, which can of course vary. It is alsoto be understood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting.

As used herein, “about” will be understood by persons of ordinary skillin the art and will vary to some extent depending upon the context inwhich it is used. If there are uses of the term which are not clear topersons of ordinary skill in the art, given the context in which it isused, “about” will mean up to plus or minus 10% of the particular term.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the elements (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. Recitation of ranges of values herein are merely intended toserve as a shorthand method of referring individually to each separatevalue falling within the range, unless otherwise indicated herein, andeach separate value is incorporated into the specification as if it wereindividually recited herein. All processes described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein, isintended merely to better illuminate the embodiments and does not pose alimitation on the scope of the claims unless otherwise stated. Nolanguage in the specification should be construed as indicating anynon-claimed element as essential.

The embodiments, illustratively described herein may suitably bepracticed in the absence of any element or elements, limitation orlimitations, not specifically disclosed herein. Thus, for example, theterms “comprising,” “including,” “containing,” etc. shall be readexpansively and without limitation. Additionally, the terms andexpressions employed herein have been used as terms of description andnot of limitation, and there is no intention in the use of such termsand expressions of excluding any equivalents of the features shown anddescribed or portions thereof, but it is recognized that variousmodifications are possible within the scope of the claimed technology.Additionally, the phrase “consisting essentially of” will be understoodto include those elements specifically recited and those additionalelements that do not materially affect the basic and novelcharacteristics of the claimed technology. The phrase “consisting of”excludes any element not specified.

In addition, where features or aspects of the disclosure are describedin terms of Markush groups, those skilled in the art will recognize thatthe disclosure is also thereby described in terms of any individualmember or subgroup of members of the Markush group.

As will be understood by one skilled in the art, for any and allpurposes, particularly in terms of providing a written description, allranges disclosed herein also encompass any and all possible subrangesand combinations of subranges thereof. Any listed range can be easilyrecognized as sufficiently describing and enabling the same range beingbroken down into at least equal halves, thirds, quarters, fifths,tenths, etc. As a non-limiting example, each range discussed herein canbe readily broken down into a lower third, middle third and upper third,etc. As will also be understood by one skilled in the art all languagesuch as “up to,” “at least,” “greater than,” “less than,” and the like,include the number recited and refer to ranges which can be subsequentlybroken down into subranges as discussed above. Finally, as will beunderstood by one skilled in the art, a range includes each individualmember.

All publications, patent applications, issued patents, and otherdocuments referred to in this specification are herein incorporated byreference as if each individual publication, patent application, issuedpatent, or other document was specifically and individually indicated tobe incorporated by reference in its entirety. Definitions that arecontained in text incorporated by reference are excluded to the extentthat they contradict definitions in this disclosure.

While certain embodiments have been illustrated and described, it shouldbe understood that changes and modifications could be made therein inaccordance with ordinary skill in the art without departing from thetechnology in its broader aspects as defined in the following claims.

What is claimed is:
 1. A process of preparing a water-based emulsionhaving an agglomerated polymer particle comprising: adding a firstmonomer feed to a reaction vessel in the presence of a first initiatorand water to form an acid-functional polymer; neutralizing theacid-functional polymer to form a primary particle; and adding a secondmonomer feed to the reaction vessel in the presence of a secondinitiator to form the agglomerated polymer particle; wherein: the firstmonomer feed comprises an unbranched (meth)acrylate monomer, a(meth)acrylic acid monomer, a branched (meth)acrylate monomer, and astyrenic monomer; the primary particle comprises a neutralizedco-polymer and has a drupelet morphology; the second monomer feedconsists of one or more hydrophobic monomers; and the agglomeratedpolymer particle comprises two or more primary particles sequestered inthe agglomerated polymer particle by the second monomer feed and has adrupelet morphology.
 2. The process of claim 1, wherein the primaryparticle has an average particle size of from about 1 nm to about 1000nm.
 3. The process of claim 1, wherein the agglomerated polymer particlehas an average particle size of from about 200 nm to about 3000 nm. 4.The process of claim 1, wherein the unbranched (meth)acrylate isselected from the group consisting of methyl methacrylate, ethylmethacrylate, n-propyl methacrylate, n-butyl methacrylate, n-amylmethacrylate, n-hexyl methacrylate, 2-n-butoxyethyl methacrylate,2-chloroethyl methacrylate, trifluoroethyl methacrylate, benzylmethacrylate, cinnamyl methacrylate, 2-ethoxyethyl methacrylate, n-octylmethacrylate, 2-phenoxyethyl methacrylate, 2-phenylethyl methacrylate,propargyl methacrylate, methyl acrylate, ethyl acrylate, n-propylacrylate, n-butyl acrylate, n-amyl acrylate, n-hexyl acrylate,2-n-butoxyethyl acrylate, 2-chloroethyl acrylate, trifluoroethylacrylate, benzyl acrylate, cinnamyl acrylate, 2-ethoxylethyl acrylate,n-octyl acrylate, 2-phenoxyethyl acrylate, 2-phenylethyl acrylate,propargyl acrylate, and combinations of two or more thereof.
 5. Theprocess of claim 1, wherein the (meth)acrylic acid monomer comprisesacrylic acid or methacrylic acid.
 6. The process of claim 1, wherein thebranched (meth)acrylate monomer is selected from the group consisting ofisopropyl methacrylate, isobutyl methacrylate, isoamyl methacrylate,2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, sec-butylmethacrylate, tertbutyl methacrylate, 2-ethylbutyl methacrylate,cyclohexyl methacrylate, cyclopentyl methacrylate, furfurylmethacrylate, hexafluoroisopropyl methacrylate, 3-methoxybutylmethacrylate, 2-methoxybutyl methacrylate, 2-nitro-2-methylpropylmethacrylate, n-octyl-methacrylate, 2-ethylpentyl methacrylate,2-ethylhexyl methacrylate, phenyl methacrylate, tetrahydrofurfurylmethacrylate, tetrahydropyranyl methacrylate, isopropyl acrylate,isobutyl acrylate, isoamyl acrylate, 2-hydroxyethyl acrylate,2-hydroxypropyl acrylate, sec-butyl acrylate, tert-butyl acrylate,2-ethylbutyl acrylate, cyclohexyl acrylate, cyclopentyl acrylate,cyclopentyl acrylate, furfuryl acrylate, hexafluoroisopropyl acrylate,3-methoxybutyl acrylate, 2-methoxybutyl acrylate, 2-nitro-2-methylpropylacrylate, n-octyl-acrylate, 2-ethylpentyl acrylate, 2-ethylhexylacrylate, phenyl acrylate, tetrahydrofurfuryl acrylate,tetrahydropyranyl acrylate, and combinations of two or more thereof. 7.The process of claim 1, wherein the hydrophobic monomer is selected fromthe group consisting of styrene, α-methylstyrene, and combinationsthereof.
 8. The process of claim 1, wherein the neutralizing comprisesadding a base to the primary particle.
 9. The process of claim 1,wherein the adding of the first monomer feed is conducted in the absenceof a surfactant.
 10. The process of claim 1 further comprising addingone or more additives selected from the group consisting of non-ionicsurfactant, biocidal agent, dispersant, pigment, fillers, defoamer,wetting agent, light stabilizer, surface-active agent, thickener,pigment stabilizer to the agglomerated polymer particle, andcombinations of two or more thereof.
 11. The process of claim 1, whereinthe adding of the first monomer feed is conducted at a temperature fromabout 30° C. to about 100° C.
 12. The process of claim 1, wherein theagglomerated polymer particle has a first glass transition temperatureof greater than −20° C. and a second glass transition temperature ofgreater than 80° C.
 13. The process of claim 1, wherein the process is aone-pot process.